Generally, π-conjugated conductive polymers whose main chains are constituted of a conjugated group containing π electrons are synthesized by an electrolytic polymerization method or a chemical oxidative polymerization method. In the electrolytic polymerization method, a mixed solution of an electrolyte to become a dopant and a precursor monomer to form a π-conjugated conductive polymer is prepared; electrodes are disposed in the solution and a supporter such as an electrode material formed in advance is immersed therein; and by applying a voltage between the electrodes, the π-conjugated conductive polymer is formed in a film shape on the supporter surface. Thus, the electrolytic polymerization method, since needing an apparatus for electrolytic polymerization, and being carried out in batch production, is inferior in mass productivity. By contrast, the chemical oxidative polymerization method has no such restriction, and can produce a large amount of a π-conjugated conductive polymer in a solution by adding an oxidizing agent and an oxidative polymerization catalyst to a precursor monomer to form the π-conjugated conductive polymer.
In the chemical oxidative polymerization method, however, the π-conjugated conductive polymer, since becoming poor in solubility in a solvent along with the growth of the conjugated group of the main chain constituting the π-conjugated conductive polymer, is obtained as a solid powder insoluble in the solvent. Hence, it is difficult to form a film having a uniform thickness of the π-conjugated conductive polymer on various types of base materials such as plastics by means such as coating. For such a reason, a method of introducing a functional group to a π-conjugated conductive polymer to make the π-conjugated conductive polymer soluble in a solvent, a method of dispersing a π-conjugated conductive polymer in a binder resin to solubilize the π-conjugated conductive polymer in a solvent, a method of adding an anionic group-containing polymer acid to a π-conjugated conductive polymer to solubilize the π-conjugated conductive polymer in a solvent, and the like have been attempted. For example, a method is known in which in order to improve the solubility of a π-conjugated conductive polymer to water, a poly(3,4-dialkoxythiophene) aqueous solution is produced by chemically oxidatively polymerizing 3,4-dialkoxythiophene in the presence of a polystyrenesulfonic acid as an anionic group-containing polymer acid having a molecular weight of 2,000 to 500,000 by using an oxidizing agent (for example, see Patent Literature 1). Further, a method is also known in which a π-conjugated conductive polymer colloid aqueous solution is produced by chemically oxidatively polymerizing a precursor monomer to form a π-conjugated conductive polymer in the presence of a polyacrylic acid (for example, see Patent Literature 2).
Further methods are also proposed in which a conductive solution miscible with an organic resin is produced by dissolving or dispersing a conductive composition in an organic solvent. As an example thereof, a solution of polyaniline in an organic solvent and its production method are known (for example, see Patent Literature 3). Further, solvent substitution methods by phase transfer from an aqueous solution containing a polyanion and an intrinsically conductive polymer to an organic solvent are also known (for example, see Patent Literatures 4, 5, 6 and 7). Further, a method is known in which an intrinsically conductive polymer after freeze-drying is dissolved in an organic solvent (for example, see Patent Literature 8). These methods, however, have such problems that as seen in the example of the polyaniline, the mixing with other organic resins is difficult and besides, the solvent group is limited to a solvent group containing a large amount of water. Even when only a small amount of water or substantially no water is contained, as seen in the above literatures (for example, see Patent Literatures 4, 5, 6 and 7), the methods have such problems that the use of an amine compound when being mixed with a resin causes the deterioration of the color tone with time, and the doping of a polyanion on a conductive polymer is gradually withdrawn by the amine and the conductivity decreases with time. Further, when a conductive polymer is mixed with an addition reaction-curable silicone resin, the method has such a drawback that an amine causes the curing inhibition and the curing of the silicone resin is insufficient.
In silicone industries, a demand is conventionally present for imparting an antistatic function to highly insulating silicone compositions in release applications and applications to pressure-sensitive adhesives. In order to meet the demand, methods have been attempted conventionally in which a carbon powder, a metal powder and an ionic conductive substance are added to silicone compositions. It is the present situation, however, that these methods do not come to satisfy many functions of the silicone resins, such as the transparency, the release performance, the tackiness performance, and the dependency of the conductivity on humidity resistance. Here, although a technology is known in which a conductive polymer in an emulsion form is mixed in a silicone resin emulsion (for example, see Patent Literatures 9 and 10), the product of the technology, since being a water dispersion, has a limit to practicability and has drawbacks such as the corrosion of devices by water and the lack of the adhesiveness.